Radiation Toxicity Flashcards
Which animals have a radiosensitivity closest to humans?
Dogs and rhesus monkeys; smaller animals are generally more radioresistant
Describe the radiation toxicity prodromal syndrome
Neuromuscular and GI symptoms
LD50 is 3-4 Gy
Supralethal dose is 8 Gy
Starts in 5-15 min and can last days (dose dependent)
What is the radiation cerebrovascular syndrome:
1) Dose
2) Death timing
3) Symptoms
1) 100 Gy
2) 24-48h
3) increased ICP due to cerebral blood vessel leakiness
What is the radiation gastrointenstinal syndrome:
1) Dose
2) Death timing
3) Symptoms
1) >10 Gy
2) 3-10 days
3) nausea/vomiting, diarrhea, sepsis
What is the radiation hematopoetic syndrome:
1) Dose
2) Death timing
3) Symptoms
1) >2.5 Gy (likely lethal after 4 Gy)
2) 30-60 days
3) pancytopenias, hemorrhage, fever/chills, mouth ulcers
What is the LD50 for humans?
3-4 Gy without medical care
4-8 Gy with standard supportive care
What is the timecourse of cytopenias?
lymphocytes drop immediately
granulocytes drop in days
platelets drop in weeks
No erythrocyte suppression
At what dose can chromosomal aberrations in lymphocytes be seen?
0.25 Gy
Is amifostine a good radioprotector?
Somewhat…it increases the LD50 in animals but must be given 30m before exposure and causes severe nausea and vomiting
What are the mechanisms of late radiation toxicities?
vascular damage, fibrosis, damage to parenchymal cells
What are “consequential late effecs”
permanent tissue damage secondary to early effects (e.g. skin necrosis requiring a graft)
What parameter impacts acute tissue effects?
total dose and longer overall treatment time (Total Gy and Gy/week)
Acute reacting tissues are not very sensitive to fraction size
What parameter impacts late tissue effects>
total Gy and Gy/fraction (sensitive to fraction sizes)
